Conventionally, stereoscopic surgical microscopes are used during surgery. In minimally invasive surgery, these instruments cannot be used and the operating medical practitioner can observe the operating site situated in a body opening only by means of an endoscope or other special aids. When performing such operations, stereo endoscopes provide additional depth information compared to conventional mono-endoscopes. Stereoscopic video endoscopes moreover enable image observation on a screen or on multiple screens and the storage of videos.
A stereoscopic video endoscope can be designed according to the principle of the rigid endoscope with two parallel beam paths. Here, two objectives arranged next to one another generate two intermediate images, which depict an object situated in front of the endoscope from different viewing angles. There is image transmission to the proximal end of the endoscope shaft by means of two parallel transmission optical units. There, images can be projected onto one or more image sensors, such as e.g. CCD- or CMOS-type image sensors.
U.S. Pat. No. 5,295,477 discloses a rigid stereo endoscope and a tube-like stereo endoscope made out of collar elements. The endoscope contains a guide or lenses in order to transmit an optical image from the end of the endoscope to a microscope connected to the endoscope. An optical waveguide contained in the endoscope transmits light from a light source into a biological specimen. A movable prism is attached to the end of the endoscope.
U.S. Pat. No. 5,527,263 discloses a rigid visual stereo endoscope with rod lenses. The endoscope contains two deflection prism pairs comprising a respective first prism coaxially with the respective optical system and a respective second prism which re-aligns the viewing axis in parallel with the optical axis. Transparent protection elements are arranged in the beam paths.
U.S. Pat. No. 4,651,201 combines a stereo endoscope containing rigid rod lenses with two cameras. The cameras transmit two stereoscopic images to two screens which are attached to a head-worn implement in front of the eyes of the user.
U.S. Pat. No. 4,862,873 discloses a video endoscope containing rigid rod lenses, comprising two image sensors, which contains an optical waveguide and an image guide. A stereoscopic image is generated by a change in the functions of the guides.
A rigid stereoscopic video endoscope with rod lens systems for image transmission is disclosed in U.S. Pat. No. 5,577,991. The video endoscope contains two parallel beam paths, in which there is image transmission by means of rod lens systems. At the proximal end of the endoscope shaft, plane mirrors direct the respective beam onto two image sensors. At the proximal end of the optical arrangement, a visual field stop is attached in the respective beam path. The visual field stops and plane mirrors can be adjusted in order to set the position of the images on the screen.
U.S. Pat. No. 6,139,490 discloses a stereo endoscope and virtual reality glasses which can be connected therewith.
U.S. Pat. No. 5,751,341 discloses a stereo endoscope comprising a plurality of shaft parts, as a result of which the shaft is rotatable.
U.S. Pat. No. 6,108,130 discloses a stereoscopic lens system and a stereoscopic image sensor with a pair of fields. A reduced distance between the images on the image sensor is obtained by an image redirection of the image information by means of the gradient lens from the image collection systems to the fields of the image sensor.
U.S. Pat. No. 6,582,358 discloses a stereo endoscope with a third beam path. The third beam path contains an optical device with a larger viewing angle than the optical devices used for stereoscopy.
U.S. Pat. No. 7,671,888 discloses a stereo endoscopic screen control device with a masking system.
U.S. Pat. No. 5,776,049 discloses a stereo endoscope with an adjustment control loop.
WO 2011/014687 A2 discloses a stereoscopic video endoscope with parallel image transmission. The image is obtained through light openings at the distal end of an endoscope shaft and transmitted in two stereoscopic partial images through the endoscope shaft to one or two outlet optical units, which project the image onto an image sensor of a camera.
The basic design of a rigid monoscopic endoscope with rod lenses emerges from the patent document U.S. Pat. No. 3,257,902. In an elongate tube, an objective and rod lens systems are arranged in succession along a common optical axis. The rod lenses serve for image guidance to the proximal end of the tube. An eyepiece, which generates a virtual image visible to the human eye, is arranged behind the proximal end of the tube. The image generated by the eyepiece can also be recorded by a suitable camera.